The present invention relates to a tap for compressed or liquefied gases, comprising a tap chamber designed in order to be fitted on a gas cylinder and enclosing a closure member at the intersection of an inlet pipe and of an outlet pipe and a means for manoeuvring the closure member.
The invention relates in particular to taps for gas cylinders or bottles which can be recharged by the user himself at a gas dispensing station. In order to fill such a cylinder correctly, observing safety regulations, it is necessary to prevent complete filling of the cylinder in order to retain, above the liquefied gas, a gaseous zone which can act as a buffer in the event of exposure of the cylinder to a heat source and, optionally, be released via a safety valve. Unfortunately, these regulations are not always observed, either due to the absence of means for monitoring filling, or through negligence on the part of the user so that the safety valve acts as the only safety measure.
There are taps in existence with a rudimentary means for monitoring the filling level. This means consists simply of a tube penetrating through the tap and provided, on the outside, with a screw or other closure means. It is the lower end of this tube which, in principle, has to define the maximum filling level on the basis of, when the level of liquid gas reaches the tube, the liquid overflowing via the tube, whereas, before, it was gas which escaped from the cylinder via the tube. Consequently, filling should be interrupted when the liquefied gas begins to emerge via the monitoring tube. Obviously, these devices lack precision and represent a source of atmospheric pollution.
Devices for automatically stopping filling do not exist to date for gas-cylinder taps. However, in other fields, for example gas tanks for motor vehicles, level-controlling valves are commonly used for automatically stopping filling when the level reaches a specific threshold. It has not been possible to use these more efficient monitoring means in gas cylinders because filling and draining of the cylinder have to take place via the same opening and because known level-controlling valves permit gas flow in only one direction.